Field of the Disclosure
The present disclosure relates to a camera module.
Discussion of the Related Art
A camera module may include an image sensor, an infrared cut-off filter configured to block light in infrared area from being incident on the image sensor, and an optical system formed of at least one lens configured to deliver an image to the image sensor.
Here, the optical system may be installed with an actuator module configured to perform auto focusing function and handshake compensation function.
The actuator module may be composed in various ways. In general, a voice coil motor is commonly used. The voice coil motor is driven by electromagnetic interaction between magnets fixed at a holder member and a coil unit wound on an outer circumferential surface of a bobbin, and may perform auto focusing function.
Generally, a yoke made of a major material of iron (Fe) that is a ferromagnetic body is provided in order to form a magnetic path of the magnet. Recently, a voice coil motor, without any separate yoke installed thereat, having an inner yoke integrally formed with a cover member such as a shield can made of iron (Fe) that is a ferromagnetic body at a position at which the yoke is to be installed, is also being developed.
Such voice coil motor having an inner yoke is advantageous in that the assembly of the camera module becomes convenient and the number of components can be reduced. However, when the length of the inner yoke is too short, the electromagnetic efficiency declines, an interference with an upper portion of the coil unit wound on an outer circumferential surface of the bobbin may occur during being driven, and foreign materials may be introduced.
In addition, when the length of the inner yoke is too long, the electromagnetic efficiency declines, as well as the verticality and concentricity becomes difficult to manage, thereby the manufacturability is degraded.